The Accreditation Council for Graduate Medical Education (ACGME) recently changed the policy governing resident work hours in the United States, potentially impacting the safety, health, and well-being of this occupational group. Percutaneous injuries (PI), with their attendant risk of hepatitis, HIV, and other blood-borne illnesses, are one of the greatest occupational hazards faced by resident physicians and motor vehicle crashes (MVC) are a leading cause of death in their age group. In our previous work, we found that extended-duration shifts (? 24 hours) are associated with a 168% increase in MVCs on the commute from work in first-year postgraduate residents (PGY1s) and a 73% increase in the risk of PI. In response to these findings, in 2011 the ACGME implemented a 16-hour limit for PGY1 work shifts. Subsequently, from July 2014-May 2017, we collected work hours, safety, health and well-being outcomes from 9,596 PGY1s on 49,418 monthly web-based reports and compared these data to those previously collected from 5,680 PGY1s (30,848 monthly reports) from 2002-2007 when PGY1s routinely worked extended-duration shifts. Under the 2011 ACGME policy, nightly hours of sleep increased, risk of an MVC decreased 25% and risk of PI decreased 44%. PGY1 well-being improved, with a 25% reduction in respiratory illness and a significant increase in exercise. Despite these improvements, the ACGME lifted these work hour restrictions in 2017. We are uniquely positioned to immediately and directly evaluate the effect of this policy change. By continuing to surveille PGY1 work hours, safety, health and well-being outcomes with our nationwide survey, we will address the NORA ?Healthcare and Social Assistance? sector and the ?Healthy Work Design and Well-Being Program? cross-sector. We will test the hypotheses that the incidence rates of MVCs, near-crashes and percutaneous injuries will be increased and resident well-being will be decreased among PGY1s working under the 2017 ACGME policy that permits extended duration shifts. Our research will ?Promote safe and healthy work design and well-being,? one of NIOSH's seven strategic goals (specifically, 7.2A and 7.2C). We plan to widely disseminate the knowledge gained by this research through planned outputs (in high- impact publications). In line with the NIOSH Research to Practice initiative, we plan to engage key stakeholders by presenting our research in national forums. As policies are changed and/or hospitals utilize the knowledge of work design garnered from this research, we expect improvements in the safety, health and well-being (end outcomes) of >100,000 resident physicians, who are the principal providers of care in academic medical centers across the US.